Apparatus and method for measuring an internal volume of a mould

ABSTRACT

An apparatus for measuring an internal volume of a mold designed for forming hollow glass containers and divisible into two or more pieces includes: a supporting element configured to support the mold pieces of the mold positioned with respective molding surfaces, delimiting the internal volume of the mold, accessible by an optical inspection device, which is configured to scan the profiles of a surface and obtain information on the distance between the surface and the optical inspection device, the scanning device being movable, relative to the supporting element, by rotation about a longitudinal axis of rotation; a control unit connected to an actuator to produce relative rotation between the optical inspection device and the supporting element.

TECHNICAL FIELD

This invention relates to an apparatus and a method for measuring aninternal volume of a mould designed for forming hollow glass containersand divisible into two or more pieces.

In general, the invention relates to an apparatus and a method formeasuring a volume inside moulds of any type; more specifically, theinvention relates to the measuring of the volume inside moulds designedfor forming glass containers (such as, for example, bottles, jars, testtubes).

BACKGROUND ART

In this field, the solutions in use comprise filling the moulds with areference liquid (for example water), after having weighed the referenceliquid (in a greater amount) and then weighing the liquid remaining and,by difference, obtaining the volume of liquid contained in the mould.

However, this approach has several problems.

Firstly, this method is not very precise because the density of thereference liquid is not known exactly.

The moulds have air vent holes which must be sealed and the jointsbetween the mould pieces must also be sealed to prevent escape of theliquid, and this operation is not easy.

Moreover, the need to wet the mould prevents easily measuring thecapacity of all the moulds produced.

Patent document US2004/017563 discloses a system for measuring variousfeatures of an object, including the volume of the object itself.

Patent document U.S. Pat. No. 6,407,818B1 discloses a system formeasuring the shape of an object in transit on a belt for being cut.

However, these patent documents do not deal in particular with theproblem of how to accurately measure the volume inside a mould having aninner surface with a double curvature, which is typical of a mould usedfor a container (for example, a glass bottle).

AIM OF THE INVENTION

The aim of this invention is to provide an apparatus and a method formeasuring an internal volume of a mould which overcome theabove-mentioned drawbacks of the prior art.

An aim of this disclosure is to provide an apparatus and a method formeasuring an internal volume of a mould which are precise and applicablein a way that is not invasive for the mould.

A further aim of this disclosure is to provide an apparatus and a methodfor measuring an internal volume of a mould which are particularly fastto execute and simple to use.

Therefore, the disclosure relates to an apparatus for measuring aninternal volume of a mould designed for forming hollow glass containersand divisible into two or more pieces.

More specifically, the mould comprises two half-moulds, comprising twopieces, each of which forms a cavity defining a moulding surface.

In general, the mould also comprises a base, constituting a third mouldpiece; the base defines a relative moulding surface, configured to formthe inside bottom wall of the moulding volume inside the mould, when thebase is coupled to the two half-moulds.

For this reason, each mould piece defines a relative moulding surface,which combines with the corresponding moulding surfaces of the othermould pieces to delimit the volume inside the mould.

The apparatus comprises a supporting element for supporting the mouldpieces (the mould pieces preferably comprise two half-moulds and a base)during the measurement.

More specifically, the supporting element is configured for supportingthe mould pieces of the mould positioned with the respective mouldingsurfaces accessible to optical inspection means.

The apparatus comprises at least one laser scanning device, for examplea so-called “profilometer”; it should be noted that the scanning deviceconstitutes an optical inspection device.

The laser scanning device is configured to scan the profiles of asurface and obtain information on the distance between the surface andthe device itself.

The apparatus also comprises a slide, to which the scanning device isconnected.

The slide is movable relative to the supporting element along alongitudinal movement axis (in the sense that at least one of the two ismovable relative to the other, preferably by translation, morepreferably along the longitudinal movement axis); the movement axis hasa predetermined geometrical relation (that is, a position) relative tothe supporting element.

Moreover, the scanning device is movable by rotation about alongitudinal axis of rotation parallel to the axis of movement, relativeto the supporting element (in the sense that at least one of the two ismovable relative to the other, preferably by rotation, and morepreferably about the longitudinal axis of rotation).

The apparatus also comprises a control unit designed for controlling themovements of the scanning device.

The control unit is connected to one or more actuators to produce arelative translation between the slide and the supporting element and arelative rotation between the scanning device and the supportingelement. The actuators are configured to reverse the direction ofmovement.

This allows the scanning device to be moved above the mould piececoupled to the supporting element, at a distance from the mouldingsurface to be scanned, for scanning, in a sequence of alternatemovements, different portions of the moulding surface.

The images acquired by the scanning device for the various portions ofthe moulding surface are made available to a processor configured tocombine them for deriving information on the profile of the mouldingsurface of the mould piece in its entirety.

The fact of scanning the moulding surfaces in a plurality of passes (forexample from one to seven passes, more preferably five for the mouldpieces consisting of the half-moulds and three for the mould piecesconsisting of the bases) is important for allowing the use of a highprecision scanning device for scanning a surface having an extensiongreater than the scanning area of the laser scanning device.

In effect, as is known, in order to obtain high scanning precision andresolution, the scanning area must be small; moreover, the rays emittedby the scanning device must be substantially perpendicular to thesurface to be scanned.

For this reason, the fact that the scanning device rotates makes itpossible to vary the inclination of the scanning device relative to thesupporting surface, to keep the rays emitted by the scanning devicesubstantially perpendicular to the moulding surface during the scanning,despite the surface being curved (the curvature may be of a particularshape, but usually the surface has a geometry which is approximatelycylindrical).

For this reason, the mould piece is connected to the supporting elementin such a way that an axis along which the mould piece is elongate ispositioned longitudinally, that is to say, parallel to the longitudinalmovement axis of the slide.

Preferably, each of the surface portions is scanned keeping theinclination of the scanning device constant and translating the scanningdevice together with the slide; at the end of each translation, in orderto scan a different surface portion, the control unit rotates thescanning device by a predetermined angle, to then perform a newtranslation (alternatively, a dual strategy may be followed, wherein thescanning device is rotated without translating it, and it is thentranslated by a predetermined quantity and a new portion of the surfaceis then scanned).

This allows a particularly precise measurement, as in the translationalmovement with a constant inclination there is greater guarantee that thedistance between the scanning device and the surface does not vary (thisis another factor which improves the precision of the measurement).

Preferably, the apparatus comprises (at least) two separate actuators, afirst actuator for translating the scanning device (that is, the slide),a second actuator for rotating the scanning device.

Preferably, the scanning device translates together with the slide.

Preferably, the slide is configured to move (by translating) relative toa frame; preferably, the supporting element is stationary (stationaryrelative to the frame) during movement of the slide.

Preferably, the scanning device is movably connected to the slide torotate relative to it.

Preferably, the slide has an arched shape with the concavity facingtowards the supporting element. This also increases the precision of themeasurement and makes it possible to keep constant both the inclinationand the distance of the scanning device relative to the surface to bescanned.

The fact of carrying out the scanning in a plurality of successivepasses means that it is necessary to subsequently make up the images ofthe scanned portions; this is not simple and could result in errors.

Therefore, the control unit is programmed to command a sequence ofmovements of the scanning device alternately along the longitudinalmovement axis and by rotation about the longitudinal axis of rotation inorder to scan a plurality of portions of the moulding surface of themould piece, so that any zone of the moulding surface is included in atleast one of the portions.

For that purpose, for reducing the probability of error and to simplifythe operations, the apparatus is equipped with a reference element,visible by the scanning device and configured to generate points ofdiscontinuity (in general meaning any geometrical element orrecognisable graphic) recognisable and present in all the images (thatis, scans) relating to the portions of the moulding surface of the mouldpiece.

Thus, this reference element is positioned in such a way as to beintercepted by the (laser of the) scanning device; moreover, thescanning device is moved in such a way as to perform a plurality ofscans of at least one portion of the reference element, at least one foreach scanned portion of the moulding surface of the mould piece.

Therefore, preferably, the apparatus comprises a reference elementlocated at a fixed position relative to the supporting element andprovided with a plurality of reference points spaced in a predeterminedmanner and configured to generate corresponding points of discontinuityin an image of the reference element itself captured by the scanningdevice.

The control unit is programmed to command a movement of the scanningdevice in the proximity of the reference element to scan at least onepart including at least one of the reference points, at the start or atthe end of the translation or rotation movements of the sequence, insuch a way that all the portions scanned of the moulding surface of themould piece include at least one of the reference points of thereference element.

Preferably, the element is aligned with the reference element along thelongitudinal movement axis, to be intercepted by the scanning device atthe start or at the end of the translation movements along the axis(movements of the scanning device together with the slide).

Preferably, the reference element is curved and the concavity faces awayfrom the supporting element (in a similar manner to the concavity of themould piece). Preferably, the reference element is shaped like a halfring.

Preferably, the reference points are angularly spaced along the halfring.

Preferably, the reference element has at least a first and a secondsurface which are offset by a predetermined known distance along aviewing path of the scanning device.

This allows a step of calibrating the scanning device, to allowcompensation of a measuring error due to variation of the distancebetween the surfaces scanned and the scanning device.

Preferably, the scanning device is movable by rotating along a circulararc having the concavity facing the supporting element; preferably, thecircular arc is defined by a guide which is integral with the slide andthe scanning device and coupled to the slide for movement along theguide, thus rotating about the longitudinal axis of rotation, whichcontains the centre of the circular arc in all the positions adopted bythe slide during its translation movement.

Preferably, the slide is in turn coupled to a guide to move along thelongitudinal movement axis.

Preferably, the guide is connected to the frame of the apparatus.

Thus, the slide is connected to the frame of the apparatus.

Preferably, the supporting element is mounted on a carriage movablealong a transversal direction (substantially perpendicular to thelongitudinal movement axis); consequently, the carriage (and with it thesupporting element) is movable along the direction transversal to theslide.

That gives the apparatus a further degree of freedom, in the relativemovement between the scanning device and the supporting element (thatis, the mould piece to be scanned).

In practice, the scanning device, relative to the supporting element(that is, the mould piece to be scanned) is movable by translating alongthe longitudinal direction (defined by the axis of longitudinalmovement), by translation along a transversal direction, and by rotationabout the longitudinal axis of rotation (parallel to the longitudinalaxis of movement).

This allows surfaces to be also scanned which have a substantially flatbase (for example, in the case of the base of the mould), without losingthe condition of being substantially perpendicular between the laserbeam of the scanning device and the surface to be scanned (usefulcondition for having a high level of precision in the measurement).

The apparatus comprises the processing means, which are programmed foranalysing the scanned images and processing them to obtain the value ofthe volume inside the mould.

More specifically, the processing means are programmed for performingthe following steps:

for each mould piece scanned, storing (at least in a temporary memory) aplurality of profiles (or images) relating to the scanned portions ofthe moulding surface;

for each mould piece scanned, combining the profiles (or images) of theplurality of profiles, to obtain a single image relating to the mouldingsurface of the mould piece;

combining the information of the profiles relating to the scannedmoulding surfaces for all the mould pieces of the mould, for calculatingthe volume inside the mould.

For this reason, this invention provides a method for measuring aninternal volume of a mould (more specifically a mould designed forforming hollow glass containers and divisible into two or more pieces).

The method comprises the following steps:

coupling at least one of the mould pieces to the supporting element insuch a way that a moulding surface of the mould piece, delimiting theinternal volume of the mould, is accessible to optical inspection means;

preparing the scanning device;

causing the scanning device to perform a sequence of movementsalternately along the longitudinal movement axis, having a predeterminedposition relative to the supporting element, and by rotation about thelongitudinal axis of rotation parallel to that movement axis, in orderto scan a plurality of portions of the moulding surface of the mouldpiece, until the scanning device has scanned the entire mouldingsurface.

Preferably, the method comprises a step of preparing a reference elementlocated at a fixed position relative to the supporting element andprovided with a plurality of reference points spaced in a predeterminedmanner and configured to generate corresponding points of discontinuityin an image of the reference element itself captured by the scanningdevice.

In light of this, preferably, the movements of the scanning devicealternately by translation along the longitudinal movement axis and byrotation about the longitudinal axis of rotation are performed in such away that all the scanned portions of the moulding surface of the mouldpiece also include at least one of the reference points of the referenceelement.

The method comprises repeating the above-mentioned scanning operations(capturing image data) for all the mould pieces which make up the mould.

In addition, the method comprises a step of processing the datacollected during the scanning (using the scanning device), for combiningit and calculating the volume inside the mould (as described above).

It should also be noted that, before the scanning, the mould pieces arecoupled to the supporting element.

In this regard, it should be noted that the apparatus comprises a singlesupporting element; in this case, the operations for scanning themoulding surfaces of the various mould pieces are performed in sequence,one after the other, after unloading the mould piece already scanned andloading the next mould piece.

Alternatively, the apparatus comprises a plurality of supportingelements, for loading the mould pieces all together.

Moreover, the supporting elements are associated with the same carriageor with two or more carriages, mobile relative to the frameindependently from each other.

The presence of a plurality of carriages reduces the time necessary formeasuring the volume in the mould, as it allows a part of the operationsfor loading a mould piece to be performed at the same time as theperformance of the operations for scanning another mould piece; in lightof this, it should be noted that the scanning operations are controlledautomatically by the control unit.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features will become more apparent from the followingdetailed description of a preferred, non-limiting embodiment of theinvention, with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a portion of the apparatus according tothis invention;

FIG. 2 is a different perspective view of the portion of the apparatusof FIG. 1;

FIG. 3 illustrates the portion of the apparatus of FIG. 2 with thescanning device in a position rotated relative to FIG. 2;

FIG. 4 illustrates the portion of the apparatus of FIG. 3 with thescanning device in a position translated relative to FIG. 3;

FIG. 5 illustrates the portion of the apparatus of FIG. 4 with thescanning device in a position rotated relative to FIG. 4;

FIG. 6 is a plan view of the apparatus of FIG. 1;

FIGS. 7 and 8 illustrate the apparatus of FIG. 6, with the scanningdevice in different operating positions.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

The numeral 1 in the accompanying drawings denotes an apparatus formeasuring an internal volume of a mould designed for forming hollowglass containers and divisible into two or more pieces 2.

Each mould piece 2 of the mould has a relative moulding surface 3,configured to delimit the volume inside the mould, when the mould piecesinteract to form the mould.

The apparatus comprises a supporting element 4 configured to support atleast one mould piece 2 or, preferably, all the mould pieces of themould.

More specifically, the supporting element 4 is shaped to support themould pieces 2 positioned with the respective moulding surfaces 3accessible to visual inspection means.

For example, the supporting element 4 has a V-shaped surface, configuredto receive and support the mould piece 2, resting with a respective backopposite the moulding surface 3. Moreover, the supporting element 4comprises stop elements for locking in position the mould piece 2 on thesupporting element 4, preventing relative movements.

Moreover, the apparatus 1 comprises a laser scanning device 5.

The scanning device 5 is of a per se known type in the prior art; it isconfigured to capture images of a surface and obtain information on thedistance between the surface and the device itself.

The apparatus 1 also comprises a slide 6 movable relative to thesupporting element 4 along a longitudinal movement axis; in practice,this means that the slide 6 is movable relative to the supportingelement 4 (for translating) in a longitudinal direction (it should benoted that the longitudinal direction is illustrated in FIGS. 6-8 byarrows).

The scanning device 5 is preferably connected to the slide 6.

In the example illustrated, the scanning device 5 is movably coupled tothe slide 6, to follow a curved trajectory, so that the scanning device5 may adopt rotated positions (with different inclinations) relative tothe supporting element 4.

In the example illustrated, the scanning device 5 is movably coupled toa guide 7 (for example a groove) defined by the slide 6, shapedaccording the curved trajectory.

For this reason, in practice, the supporting element is movable byrotation about a longitudinal axis (referred to hereafter as axis ofrotation) parallel to the axis of movement.

This configuration facilitates the scanning of moulding surfaces havingan elongate shape; in effect, operatively, the mould piece 2 ispositioned on the supporting element 4 in such a way that it is elongatealong the longitudinal direction.

For this reason, the translational movement (of the slide 6) moves thescanning device 5 along the mould piece 2 according to the longitudinalextension of the piece. On the other hand, the rotational motion makesit possible to orient the scanning device 5 substantiallyperpendicularly to a predetermined portion of the moulding surface 3 ofthe mould piece 2.

If the moulding surface 3 of the mould piece 2 has a substantiallycylindrical geometry, the condition of being substantially perpendicularremains during the movement of the scanning device 5 for longitudinaltranslation.

Moreover, the apparatus 1 comprises a control unit (not illustrated, ofper se known type, consisting for example of a suitably programmedelectronic card).

The control unit is connected to movement means configured to produce arelative translation between the slide 6 and the supporting element 4and a relative rotation between the scanning device 5 and the supportingelement 4.

In principle, these movement means also comprise a single actuator,because the above-mentioned translation and rotation movements arepreferably uncoupled from one another (that is to say, they are notperformed at the same time, but in succession).

However, preferably, the movement means comprise a first actuator(preferably of an electromechanical type), to move the slide 6longitudinally, and a second actuator (preferably of a pneumatic type oran electric motor, for example a stepping motor), for moving thescanning device 5 by rotation (that is to say, along the curved path).

Moreover, preferably, the apparatus comprises a reference opticalelement (for example an optical ruler preferably defined by a linearencoder), positioned along the longitudinal direction of translation ofthe slide.

The purpose of the optical reference element is to provide the time ofthe acquisitions; that is, during the translation along the longitudinalmovement axis, the scanning device makes a plurality of acquisitions(which make up a portion of the moulding surface), in succession; theinstants of acquiring the plurality of acquisitions are determined (bythe control unit) as a function of the optical reference element.

Thus, the control unit is connected to the first and second actuatorsfor controlling the movements according to a predetermined logic (withwhich the control unit is programmed, that is to say, stored in thecontrol unit).

More specifically, the control unit is programmed to command a sequenceof movements of the scanning device 5, alternatively:

along the longitudinal movement axis and

by rotation about the longitudinal axis of rotation.

The control unit is programmed to command the movement of the scanningdevice 5 (relative to the supporting elements 4; it should be noted thatit is always possible, in theory, to keep the scanning device 5stationary and move the supporting element 4, to obtain the samerelative movements), in the sequence of movements, for scanning aplurality of portions 8 of the moulding surface 3 of the mould piece 4,in such a way that any zone of the moulding surface 3 is within at leastone of the portions 8.

In the example illustrated, the portions 8 are elongate longitudinally.

This is the result of a programming logic of the control unit, whichcomprises performing the rotations when the device 5 is deactivated andkeeping the device 5 active (that is, in a profiles capturing mode)during the longitudinal translation movements.

Preferably, the programming logic of the control unit comprisesperforming the rotations when the scanning device 5 is positioned on theside of one of the ends of the mould piece 2.

It should be noted that there is also an alternative programming logicof the control unit, wherein the translations of the scanning device 5occur when the scanning device 5 is deactivated and the rotations occurwhen the scanning device 5 is active; in this case, the surfacescorresponding to the portions 8 are transversal to the axis along whichthe mould piece 2 extends.

Preferably, the apparatus 1 comprises a reference element 9, comprisinga predetermined geometry (and known to the apparatus 1 itself).

The reference element 9 is operatively positioned in a fixed positionrelative to the supporting element 4.

The reference element 9 is equipped with a plurality of reference points10 spaced in a predetermined manner on the reference element 9.

These reference points 10 are configured to generate correspondingpoints of discontinuity in an image of the reference element 9 capturedby the scanning device 5 (for example, they are produced by notches orgeometrical shapes which can be detected by the profilometer (that is,by the scanning device) or by means of zones of chromatic contrast or bypassage from light to dark).

The control unit is programmed to command a movement of the scanningdevice 5 in the proximity of the reference element 9 for scanning atleast a part comprising at least one of the reference points 10.

More specifically, the control unit is programmed to command themovement of the scanning device 5 in the proximity of the referenceelement 9 (for scanning at least a part comprising at least one of thereference points 10) at the start or at the end of the translation orrotation movements of the sequence, in such a way that all the scanscorresponding to the scanned portions 8 of the moulding surface 3 of themould piece 2 comprise (in terms of scanned profile) at least one of thereference points 10 of the reference element.

Preferably, the reference element 9 has the shape of a half ring and thereference points 10 are angularly spaced along the half ring.

Preferably, the reference element 9 has a surface 11 offset by apredetermined known distance (along a viewing path of the scanningdevice) relative to at least one other surface of the reference element9.

For example, the reference element 9 has an annular surface 11 spaced(forming a step) from another annular surface 12 defining the referencepoints 10.

Preferably, the supporting element 4 is mounted on a carriage 13.

The carriage is movable along a transversal direction, perpendicular tothe longitudinal movement axis; consequently, the carriage 13 is movablealong the direction transversal to the slide 6.

More specifically, the carriage 13 is mounted on tracks 14 (or otherguide means) which are transversal to the longitudinal direction oftranslation of the slide 6.

The tracks are connected to a frame (for resting on the ground) of theapparatus (not illustrated).

Preferably (in an embodiment not illustrated), the apparatus 1 comprisestwo or more of the carriages 13.

For this reason, the invention provides a method for measuring aninternal volume of a mould; more specifically, of a mould designed forforming hollow glass containers and divisible into two or more pieces 2.

The method comprises the following steps:

coupling a piece 2 to the supporting element 4;

moving the supporting element 4 (using the carriage 13) to position itin a working area in which the scanning device 5 is active;

causing the scanning device 5 to perform a sequence of movementsalternately along the longitudinal movement axis and by rotation aboutthe longitudinal axis of rotation, in order to scan a plurality ofportions 8 of the moulding surface 3 of the mould piece 2, until thescanning device has scanned the entire moulding surface.

More specifically, during the execution of a sequence of movements ofthe scanning device 5, the scanning device 5 is kept:

active (to capture images of a scanned surface), during the movements bylongitudinal translation (along the direction of extension of the mouldpiece 2), and

deactivated during the movements by rotation,

or vice versa.

It should be noted that the movements by longitudinal translation arealso alternated with movements by transversal translation (using themovement carriage 13 of the supporting element 4), as an alternative tothe above-mentioned movements by rotation (this to allow scanning of thebase of the mould, for example, or of other surfaces having particulargeometries).

In any case, preferably, the movements of the scanning device 5alternately by translation along the longitudinal movement axis and byrotation about the longitudinal axis of rotation (or by translationalong a transversal direction) are performed in such a way that all theportions 8 scanned of the moulding surface 3 of the mould piece 2include at least one of the reference points 10 of the reference element9.

What is claimed is:
 1. An apparatus for measuring an internal volume ofa mould designed for forming hollow glass containers and divisible intotwo or more pieces, the apparatus comprising: a supporting element,configured to support the mould pieces positioned to allow respectivemoulding surfaces, delimiting the internal volume of the mould, to beaccessible for optical inspection; an optical inspection device,configured to scan profiles of a surface and obtain information on thedistance between the surface and the device itself, wherein the opticalinspection device and the supporting element are movable relative to oneanother, by rotation about a longitudinal axis of rotation; a controlunit connected to one or more actuators to produce a relative rotationbetween the optical inspection device and the supporting element; areference element located at a fixed position relative to the supportingelement and provided with a plurality of reference points spaced in apredetermined manner and configured to generate corresponding points ofdiscontinuity in an image of the reference element captured by theoptical inspection device, wherein the reference element is curved andhas a concavity facing away from the supporting element, and wherein thecontrol unit is programmed to command a relative rotation between thereference element and the optical inspection device, to scan at leastone part including at least one of the reference points.
 2. Theapparatus according to claim 1, wherein the control unit is programmedto command a sequence of movements of the relative rotation between thesupporting element and the optical inspection device, by rotation aboutthe longitudinal axis of rotation, in order to scan a plurality ofportions of the moulding surface of the mould piece, so that any zone ofthe moulding surface is included in at least one of the portions.
 3. Theapparatus according to claim 2, wherein the control unit is programmedto command the optical inspection device to scan the at least one partincluding the at least one of the reference points, at the start or atthe end of the translation or rotation movements of the sequence, insuch a way that all the scans of the portions of the moulding surface ofthe mould piece include at least one of the reference points of thereference element.
 4. The apparatus according to claim 3, wherein thereference element has the shape of a ring and the reference points areangularly spaced along the ring.
 5. The apparatus according to claim 3,wherein the reference element has at least a first and a second surfacewhich are offset by a predetermined known distance along a viewing pathof the scanning device.
 6. The apparatus according to claim 1, whereinthe scanning device is movably coupled to a slide to rotate about thelongitudinal axis of rotation.
 7. The apparatus according to claim 1,wherein the scanning device is relatively movable with respect to thesupporting element, by rotation.
 8. The apparatus according to claim 1,comprising a slide coupled to a guide to move along a longitudinalmovement axis.
 9. The apparatus according to claim 1, wherein thesupporting element is mounted on a carriage which is movable along atransversal direction, perpendicular to a longitudinal movement axis.10. The apparatus according to claim 1, wherein the optical inspectiondevice is stationary and the supporting element is movable with respectto the optical inspection device.
 11. The apparatus according to claim10, wherein the supporting element is actuated to undergo a sequence ofmovements, so that a plurality of portions of the moulding surface ofthe mould piece are scanned.
 12. The apparatus according to claim 11,wherein scanned portions are elongate longitudinally.
 13. The apparatusaccording to claim 1, wherein the control unit is programmed for keepingthe optical inspection device deactivated during the rotation movement.14. The apparatus according to claim 1, wherein the predeterminedgeometry of the reference element is known to the apparatus.
 15. Theapparatus according to claim 1, wherein the reference points of thereference element include geometrical shapes which can be detected bythe optical inspection device.
 16. The apparatus according to claim 1,wherein the reference points of the reference element include zones ofchromatic or darkness contrast, which can be detected by the opticalinspection device.
 17. The apparatus according to claim 1, wherein thereference element has an annular surface spaced from another surfacedefining the reference points.
 18. An apparatus for measuring aninternal volume of a mould designed for forming hollow containers anddivisible into two or more pieces, the apparatus comprising: asupporting element, configured to support the mould pieces positioned toallow respective moulding surfaces, delimiting the internal volume ofthe mould, to be accessible for optical inspection; an opticalinspection device, configured to scan profiles of a surface and obtaininformation on the distance between the surface and the device itself,wherein the optical inspection device and the supporting element aremovable relative to one another, by rotation about a longitudinal axisof rotation; a control unit connected to one or more actuators toproduce a relative rotation between the optical inspection device andthe supporting element; a reference element located at a fixed positionrelative to the supporting element and provided with a plurality ofreference points spaced in a predetermined manner and configured togenerate corresponding points of discontinuity in an image of thereference element captured by the optical inspection device, wherein thereference element is curved and has a concavity facing away from thesupporting element and has an annular surface spaced from anothersurface defining the reference points, and wherein the control unit isprogrammed to command a relative rotation between the reference elementand the optical inspection device, to scan at least one part includingat least one of the reference points.
 19. A method for measuring aninternal volume of a mould designed for forming hollow glass containersand divisible into two or more pieces, wherein the method comprises thefollowing steps: coupling at least one of the mould pieces to asupporting element in such a way that a moulding surface of the mouldpiece, delimiting the internal volume of the mould, is accessible foroptical inspection; preparing an optical inspection device configured tocapture images of a surface and obtain information on the distancebetween the surface and the device itself; causing a sequence ofrelative movements, by rotation about a longitudinal axis of rotation,between the supporting element and the optical inspection device, inorder to scan a plurality of portions of the moulding surface of themould piece, until the optical inspection device has scanned the entiremoulding surface, wherein a reference element located at a fixedposition relative to the supporting element and provided with aplurality of reference points spaced in a predetermined manner andconfigured to generate corresponding points of discontinuity in an imageof the reference element captured by the scanning device, wherein thereference element is curved and has a concavity facing away from thesupporting element, and wherein a relative rotation between thereference element and the optical inspection device is provided, to scanat least one part including at least one of the reference points. 20.The method according to claim 19, wherein the relative movements betweenthe reference element and the of the optical inspection device areperformed alternately by translation along a longitudinal movement axisand by rotation about the longitudinal axis of rotation, in such a waythat all the scans comprising the portions of the moulding surface ofthe mould piece also include at least one of the reference points of thereference element.